This application claims priority to Japanese application serial number 2000-283964, which application is hereby incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to reciprocating cutting tools, such as jigsaws, that have a reciprocating saw blade for cutting workpieces.
2. Description of the Related Art
Known jigsaws comprise a rotating electric motor as a drive source and a motion conversion mechanism that converts the rotation of the motor into linear reciprocating movement of a blade. Japanese Laid-Open Utility Model Publication No. 4-54801 teaches a motion conversion mechanism for a jigsaw and this mechanism will now be described with reference to FIG. 6, which substantially corresponds to FIG. 1 from that Japanese publication.
As shown in FIG. 6, a jigsaw 100 includes a motion conversion mechanism 101 that has a crank disk 104. The crank disk 104 is rotatably driven by an electric motor 102 via an intermediate gear 103. A guide roller 105 is mounted on the crank disk 104 in a position displaced from the center of rotation of the crank disk 104. Therefore, the guide roller 105 revolves around the rotational axis of the crank disk 104, while the guide roller 105 also can rotate around its own axis. The guide roller 105 engages a horizontal engagement recess formed in a slider 107 that is fixed onto a vertical rod 106. Therefore, as the crank disk 104 rotates, the guide roller 105 reciprocally moves along the horizontal recess of the slider 107. Thus, the guide roller 105 imparts to the rod 106 a vertical reciprocating component of the rotating movement of crank disk 104. However, the horizontal reciprocating component of the rotating movement of the crank disk 104 is not imparted to the rod 106. Therefore, the rod 106 linearly reciprocates in the vertical direction with respect to the workpiece and the jigsaw 100.
A rod holder 108 vertically slidably supports the rod 106. An upper end of the rod holder 108 is connected to the body of the jigsaw 100 and can pivot about a horizontal axis by means of a pivot shaft 108a. A compression spring 109 serves to bias the lower portion of the rod holder 108 in a rearward direction, which direction is opposite to the moving direction (forward direction) of the jig saw 100 during the cutting operation.
A cam plate 110 is mounted on the intermediate gear 103. A biasing roller 111 is coupled to the cam plate 110, such that the biasing roller 111 reciprocates in the horizontal direction (forward and rearward directions) as the cam plate 110 rotates. Therefore, the blade B mounted on the lower end of the rod 106 is reciprocally pressed forwardly by the biasing roller 111, as the cam plate 110 rotates. The biasing force of the biasing roller 111 counters or opposes the biasing force of the compression spring 109.
According to this arrangement, because the rod holder 108 is pivotally supported by the pivot shaft 108a, the blade B may be prevented from twisting during the cutting operation and the blade B can reciprocally move both in the vertical direction and the forward and rearward directions. That is, the blade B can substantially move in an orbital path with respect to the workpiece and the jigsaw 100.
However, problems exist with the design of the known jigsaw 100. For example, because the slider 107 pivots forward and rearward together with the rod 106, a clearance must be provided between the horizontal engagement recess of the slider 107 and the guide roller 105 in order to permit the slider 107 to incline relative to the guide roller 105. Because of the presence of such a clearance, the guide roller 105 cannot move smoothly along the engagement recess of the slider 107. Instead, the guide roller 105 will oscillate in the vertical direction between the upper and lower edges of the slider 107. The motion conversion mechanism 101 will generate vibrations and sounds, due to the guide roller 105 repeatedly contacting and rattling between the edges of the slider 107. Because these vibrations will be transmitted to the operator who is holding the jigsaw 100 while performing a cutting operation, the vibrations may fatigue the operator.
Another known motion conversion mechanism for a jigsaw is taught in U.S. Pat. No. 3,236,111. This conversion mechanism also utilizes a slider that engages a guide roller. Thus, the slider will reciprocate in the vertical direction as the guide roller revolves. However, a rod, on which a blade is mounted, is connected to the slider such that the rod can pivot relative to the slider in the forward and rearward directions. In addition, in order to reciprocate the rod (or the blade mounted on the rod) in the forward and rearward directions, the slider moves in the forward and rearward directions as the slide moves vertically. Therefore, during the cutting operation, the slider may receive a reaction force from a workpiece via the blade and the rod. As a result, the slider will pivot or incline relative to the guide roller and the guide roller will not smoothly move relative to the slider.
It is, accordingly, one object of the present invention to teach improved reciprocating cutting tools. For example, in one aspect of the present teachings, vibrations and noise may be reduced during the cutting operation.
According to one embodiment of the present teachings, a reciprocating cutting tool may include a slider that can reciprocate linearly in a first direction. A rod or blade shaft holder is movable with the slider in the first direction and is supported by the slider, such that the rod or blade shaft holder is movable in a second direction that is different from the first direction. A blade can be mounted on the rod (blade shaft holder) and the rod (blade shaft holder) is movable in the second direction independently of the movement of the slider in the first direction.
In a preferred embodiment, the first direction is a vertical direction with respect to a workpiece and the second direction is a horizontal direction (i.e., forward and rearward directions) of the workpiece. The blade may be moved in the forward direction to cut the workpiece during the cutting operation. Thus, the blade may substantially move along an orbital path with respect to the workpiece during the cutting operation.
Because the rod (blade shaft holder) is movable in the second direction independently of the movement of the slider in the first direction, the slider only moves in the first direction and preferably the slider does not move or incline in the second direction. Therefore, rattling is preferably reduced between the slider and a drive mechanism, which may be included within a motion conversion mechanism, because the motion conversion mechanism preferably does not move in the second direction. As a result, vibrations and noise that result from such rattling may be considerably reduced.
According to another embodiment of the present teachings, reciprocating cutting tools, such as a jig saw, may include a motor generating a rotational output, which rotational output is ultimately utilized to drive a blade in an orbital path with respect to a workpiece. A first means may be provided for converting the rotational output of the motor into linear reciprocating movement in a first plane. A second means also may be provided for transmitting the linear reciprocating movement to the blade. The second means may be, e.g., pivotally coupled to the first means and fixedly coupled to the blade. Preferably, the second means can reciprocate in the first plane and in a second plane that is substantially perpendicular to the first plane. Thus, the blade may preferably move an orbital path within the second plane. However, the first means preferably does not substantially move in the second plane.
In another embodiment, the first plane may comprise a vertical cutting direction with respect to the workpiece. Further, the second plane may comprise (i) a forward direction for pressing the blade against the workpiece during the cutting operation and (ii) a rearward direction opposite to the forward direction. In another embodiment, the first means may comprise a slider that is slidably received within a guide block. Preferably, the slider can slide with respect to the guide block in the first plane, but the guide block prevents the slider from inclining or rattling in the second plane. The guide block may optionally be fixed in position within respect to a housing of the cutting tool.
A support pin may pivotally couple the first means to the second means. Optionally, a pair of bearings may rotatably support the support pin. The second means may include a rod (or blade holder shaft) that is prevented from rotating about a longitudinal axis of the rod (blade shaft holder), for example, by a fixed bush. A biasing roller may contact the blade or the blade mounting shaft in the second plane, so as to reciprocally move in the second plane in synchronism with the reciprocating movement of the first means in the first plane.
In another embodiment of the present teachings, reciprocating cutting tools may include a motor that generates a rotational output, which rotational output may be utilized to drive the blade in an orbital path with respect to the workpiece. A motion conversion mechanism may be coupled to the motor, so as to convert the rotational output into a substantially linear output. Further, a slider may be coupled to or incorporated within the motion conversion mechanism. Preferably, the slider linearly reciprocates in a first plane when the motor is driven, but substantially does not move in a second plane that is substantially perpendicular to the first plane. A blade mounting shaft may be pivotally coupled to the slider. Preferably, the blade mounting shaft reciprocates in the second plane in order to impart an orbital cutting motion to the blade.
The present teachings also provide means for biasing the blade mounting shaft, or a blade attached to the blade mounting shaft, in the second plane. In addition, the present teachings further provide means for preventing the blade (or the blade mounting shaft) from rotating or twisting during a cutting operation.
Additional objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.